Linear electric motors are well known and used in various branches of industry and in transport. Among the main advantages of such motors, practically complete elimination from the electric driving system of intermediate mechanical, hydraulic and similar devices for transforming rotary motion into translational one is to be noted.
Such an arrangement results in an increase in the drive reliability as a whole and allows the existing possibilities of automatic control circuits to be completely utilized, which possibilities are impossible to be realized at the modern level of production technology of such transforming devices.
However, the experts dealing with the development of linear electric motors and especially those utilizing the principle of combining armature and field windings, are facing the problem of increasing the degree of utilization of their active materials.
Known in the art are linear motors (USSR Author's Certificate No. 192895, Int. Cl. H 02n, published Mar. 2, 1967) whose design allows this problem to be solved to a certain extent. Said motor comprises a stator whose magnetic core is formed by two equidistant strips made of a ferromagnetic material. Each strip is provided with uniformly alternating projections and recesses, disposed in a row along the strip. The ferromagnetic strips are so arranged that the projections of one strip are facing those of the other one. Said projections are designed to give the main magnetic field of the motor a certain shape, and for this reason they will be hereinafter referred to as a pole-forming projections. Between the above described strips is disposed a movable core which, when the motor is used e.g. in a machine tool, sets in motion its working tool. The movable core is so constructed that it consists of alternating regions having high and low magnetic permeability.
Each of the magnetic cores of the stator is constructed in the form of cogged stacks of electrical steel with elements of an excitation system disposed therebetween, said elements being permanent magnets. These magnets are connected in series in an external excitation circuit, i.e. the north pole of one magnet is turned towards the south pole of the other magnet. The magneto-motive forces developed by these magnets are directed in accordance with one another and cross the movable core in the transverse direction.
On both the magnetic cores of the stator are laid armature windings, each being divided into two coil groups having equal number of sections. The number of these windings can be any.
The above described design of the linear electric motor, alongside with obvious advantages consisting in great savings of copper, is characterized by a low efficiency which is caused by the fact that a portion of active sides of the armature windings, disposed opposite the regions of the movable core which have low magnetic permeability, is flown round by the current but does not take part in the development of the tractive force.